Pressure regulators and, in particular, pilot operated pressure regulators are well known. Such pressure regulators typically include a pressure air input, a vent and two solenoids. One of the solenoids is commonly called an up solenoid and the other solenoid is commonly called a down solenoid. The solenoids regulate the input and vent, respectively, to carefully control a pilot signal pressure.
Oftentimes, an electronic pressure sensor is provided to monitor the pilot signal pressure. A computer, such as a microprocessor, controls the up and down solenoid positions in response to feedback from the pressure transducer to achieve a desired output pressure.
The U.S. Pat. No. 3,878,376 to Sholes, Jr. et al. discloses a computer-operated solenoid valve pressure control system having a number of solenoids which connect sources of pressurized gas, an atmospheric vent and a source of vacuum to pressure a volume. A pressure transducer senses the pressurized volume pressure and provides feedback to a computer controller. The pressurized volume is coupled to a pilot input signal of a pilot operated pressure regulator.
The U.S. Pat. No. 4,644,848 to McKendrick discloses an electro-pneumatic pressure regulator which utilizes a microprocessor to control a current to a pressure transducer which, in turn, supplies a pneumatic output signal to a pressure-to-pressure booster regulator.
The U.S. Pat. No. 4,394,871 to Czajka et al. discloses a programmable pressure regulator which is used in a metal forming operation. The system generates a regulated pressure in a line which has an input controlled by a solenoid connected to a source of pressurized gas and atmospheric vents regulated by solenoids. The line is connected to a cavity wherein a pressure transducer senses the pressure therein. The various solenoids and the pressure transducer are coupled to a comparator circuit which may be an analog device to regulate the solenoids in order to achieve a predetermined pressure time cycle.
Other patents of a more general interest include the U.S. Pat. Nos. to Clardy et al 3,348,032, Klem et al 3,794,070, Kawamura et al 4,477,183, Groeschner 4,512,362, McKendrick 4,680,441 and Appleby 4,718,454.
One problem with the methods and systems described by the prior art is the inability to match command or reference signals with the transducer feedback signal due to varying system operating conditions, such as heating, wear, varying lubrication levels, contamination, uneven or nonlinear operation and the like. The prior art methods and systems are also unable to compensate for different size solenoids, different types of regulators, different devices being controlled, different load levels wherein pressure is changing and uneven loads when the pressure is changing.